Abstract: Objective A novel Smac-mimic polypeptide(SmacN7) was designed and synthesized to study its biological activity that promotes apoptosis of bladder cancer cells. Methods SmacN7 was synthesized with aid of polypeptide solid phase synthesis technique,purified with reverse-phase HPLC and identified with mass spectrometry.Using fluorescent microscopy,MTT assay and flow cytometry,the apoptosis effect on bladder cancer T24 cell line with low-dosage of MMC was evaluated. Results The peptide was more than 95% in purity and the measured value of molecular weight was conformed to it s theoretical value. Typical apoptosis morphological changes of the cells were detected af ter being incubated by 50～500μg/ L SmacN7 for 12～48 h. With the increase of concent ration of SmacN7 or the prolongation of the t reating time, the proliferation inhibitory ratio of the cancer cells increased by (9. 62 ±1. 07) %～ (61. 48±1. 15) %、(24. 17 ±1. 02) %～ (72. 86 ±1. 68) %、(43. 24 ±1. 15) %～ (84. 91 ±1. 74) % and the percentage of apoptosis increased by (6. 12 ±1. 16) %～ (49. 81 ±2. 11) %、( 13. 47 ±1. 15) %～ ( 64. 54 ±2. 27) %、(28. 91 ±1. 08) %～ (82. 36 ±2. 15) % when t reated for 12 、24 、48 h respectively. Conclusion 　The collected fusion peptide SmacN7 is the target peptide with high purity and can be stably t ransferred into T24 cells and effectively utilized. It clearly has the biological activity in promoting apoptosis of bladder cancer T24 cell lines with the induction of low2dosage of MMC. These result s accumulate valuable data for the biological therapy of bladder cancer.